Light emitting diodes (LEDs) are becoming more and more popular for lighting and signaling applications, in which multiple LEDs are formed into an array and powered to emit light. LED arrays are typically supplied with DC current with the amount of supplied power controlling the array brightness. In many applications, it is desirable to maintain electrical isolation between the LED array and the input power supply, such as where installers may ground the LED array to earth ground. Moreover, it is desirable to avoid thermal excesses in the LED power source. A need therefore exists for improved LED power sources and DC-DC converters that provide isolation and self-protection against overheating.